1. Field of the Invention
The present invention relates to a microwave oven, and more particularly, to a damping device in a microwave oven for regulating an air flow to a cooking chamber.
2. Background of the Related Art
The microwave oven is an appliance for disturbing an array of water molecules in food by means a microwave as a heat source, to generate a heat caused by friction between the molecules, for cooking food. The microwave oven has a convection function in which food is cooked, or a surface of food is browned by a heat from a heater, together with the microwave oven function. As shown in FIG. 1, the microwave oven is provided with a body 10, a cooking chamber 20 in one side portion of the body 10 for cooking, an electrical compartment 30 in the other side portion of the body for fitting various components required for driving the device, and a partition wall 40 for partitioning the cooking chamber and the electrical compartment 30. The electrical compartment 30 is provided with a magnetron 31 for generating a microwave, a transformer 32 for transforming a utility voltage to a voltage required for the magnetron, a cooling fan 33 for cooling the magnetron, and an air duct 34 for guiding an air flow caused by rotation of the cooling fan to a pass through hole(see 41 in FIG. 2A) in the partition wall 40 into the cooking chamber. And, there is a heater(not shown) for generating a heat when the convection function is selected.
In the meantime, during the cooking by using the convection function when the cooking is conducted by using a heat from the heater, the microwave oven can not conduct the convection function properly since the air flow from the cooling fan 33 comes into the cooking chamber 20 through the air duct 34 and drops a temperature of the cooking chamber 20 heated by the heater. In order to block the air flow from the cooling fan 33 to the cooking chamber 20, a damping device is disclosed in Korean Patent No. 99-35944 for selective blocking of the air duct.
As shown in FIGS. 2A and 2B, the damping device disclosed in Korean Patent No. 99-35944 is provided with a damper 51 rotatably fitted in the air duct 34 for blocking the air flow toward the cooking chamber, and bidirectional motor 52 fitted to the air duct and coupled with the damper for rotating the damper 51. There is also a microswitch 53 fitted to one side of the air duct 34 for providing a control signal to a microcomputer(not shown) to control operation of the bidirectional motor 52, a push button 54 projected from one end of the damper 51 for pressing the microswitch when the damper rotates, and a stopper 55 fitted to a pass through hole 41 side of the partition wall inside of the air duct for stopping rotation of the damper.
The operation of the foregoing damping device will be explained.
First, as shown in FIG. 2A, in a convection mode, a regular direction rotation(rotation in a clockwise direction) of the damper 51 by the bidirectional motor 52 until an end 51 a thereof is stopped by the stopper 55 blocks the air duct 34. Then, the damper blocks the air duct so that the air flow can not come into the cooking chamber 20, thereby conserving the heat from the heater within the cooking chamber. And, at a moment the air duct 34 is blocked by the damper 51, the push button 54 is caused to press the microswitch 53, a signal generated at this moment is provided to the microcomputer, to stop operation of the bidirectional motor 52.
Second, as shown in FIG. 2B, in a microwave mode, the damper 51 is rotated in a reverse direction(a rotation in an anti-clockwise direction) by the bidirectional motor 52, to open the air duct 34. According to this, the air flow from the cooling fan 33, moves in the air duct, enters into the cooking chamber 20 through the pass through hole 41 in the partition wall 40, and carries vapor in the cooking chamber 20 away from the microwave oven. And, when the air duct 34 is opened as the damper 51 is moved, the push button 54 is freed from the microswitch 53, and a signal generated in this instance is provided to the microcomputer(not shown), and the microcomputer stops the bidirectional motor 52.
However, the aforementioned related art damping device has the following problems.
First, in the related art damping device, the bringing into contact of the push button 54 to an actuator 53a in the microswitch 53 during the rotation of the damper may cause to provide an excessive force to the actuator 53a or generate noise. That is, referring to FIG. 2A, it can be known that an extent of actuator 53a pressing is dependent on a position of the stopper 55 fitting. Because there may be fabrication errors between components, inclusive of the push button 54 on the damper 51, the stopper 55 on the partition wall 40. For an example, if the stopper 55 is fitted closer to the pass through hole 41 side owing to a fabrication error, the damper 51 stops before the push button 54 presses the actuator 53a, which makes control of the bidirectional motor impossible. However, since the damping device becomes inoperative if the bidirectional motor is not controllable, the stopper is in general fitted to a place away from the pass through hole side. Consequently, since the damping device comes to a stop after the push button presses the actuator, excessively(see a dashed line in FIG. 2A), it is liable that an excessive pressure is provided to the microswitch 53. Moreover, since various mating components are fitted to different members for use in controlling operation of the bidirectional motor 52, the liability that an excessive pressure is provided to the microswitch 53 becomes further higher after an assembly. That is, the fabrication error in the assembly of the partition wall 40 having the stopper 55 fitted thereto, the damper 51 having the push button 54 fitted thereto, and the air duct 34 having the microswitch 53 fitted thereto may make the liability further higher. Consequently, the excessive pressure to the microswitch 53 may cause problems, not only in a driving performance of the microswitch itself, but also in noise occurrence, or in a lifetime of the microswitch 53 coming from an excessive contact between the push button 54 and the microswitch 53.
Second, the mounting of the bidirectional motor 52 to an upper part of outside of the air duct 34 in the related art damping device is limited by an oven lamp(not shown) and an upper case 11 in view of space, which prolongs the assembly process, and makes an interchangeability with other large sized components poor, that results in a high cost.
Third, the direct coupling of the damper 51 with the bidirectional motor 52 in the related art damping device fixes a direction of rotation of the damper only by the motor. That is, a regular direction rotation of the damper requires a regular direction rotation of the motor, and a reverse direction rotation of the damper requires a reverse direction rotation of the motor, no motor, but the bidirectional motor, can be used. The use of the bidirectional motor 52 results in a high cost and complicate system.
Accordingly, the present invention is directed to a damping device in a microwave oven that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a damping device in a microwave oven, which has a smooth operation and a low cost.
Another object of the present invention is to provide a damping device in a microwave oven, which can eliminate an excessive pressure to the microswitch.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the damping device in a microwave oven includes an air duct on an electrical compartment side of a partition wall for guiding an air flow from a cooing fan to a cooking chamber, a damper rotatably hinged on the air duct for selectively blocking the air duct, a driving cam having a relative thickness difference between a thick portion and a thin portion, rotatable in contact with one end of the damper for pressing the one end of the damper to rotate the damper centered on the hinge owing to the thickness difference, and control means for controlling rotation of the driving cam.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.